The present invention pertains to a device for detecting gaseous and vaporous components of a gas mixture by using optically perceptible reaction zones in channels which are located next to one another on a support, are connected in parallel, are arranged between a gas inlet and a gas outlet, and are exposed to the component to be detected along a flow axis following the course of the channel, and with a scanning section of a scanning device, which scanning section extends along at least one of the channels.
A device of the above-described type has become known from DE-C39,02,402. In the prior-art device, channels extending in parallel on a chip-like support are provided, wherein gas can flow through the channels from a gas inlet to a gas outlet, and on the inside, which acts as a reaction zone, the channels contain a substance which reacts with the component to be detected. The gas flows through the channels along a flow axis that follows the course of the channel and covers the gas inlet and the gas outlet in an aligned manner.
The individual channels may be connected in parallel in terms of flow to make possible the simultaneous detection of the individual components of the gas mixture. To evaluate the change in color, which has taken place in the individual channels due to the reaction of the substance with the component to be detected, the support is pushed into an optoelectronic scanning device, which makes possible the scanning of the length of the layer whose color has changed in the individual channels. The individual channels are brought one after another into the range of action of the optoelectronic scanning device by means of feed rollers, with which a displacing movement of the support is performed, and they are evaluated. The optoelectronic scanning device is designed essentially such that individual LEDs with corresponding detectors, e.g., 6 LEDs, with which the length of the zone whose color has changed is determined, are arranged along the flow axis of the channel to be evaluated. Channels connected in parallel are frequently used when the composition of the gas mixture is unknown, and the type of the substance of the individual components must first be determined. The concentration of the components in the gas sample is initially of secondary importance here.
If such an analysis is to be performed with the prior-art device, the individual channels, which already have the optically detectable reaction zones as a consequence of the parallel admission of the gas, must be brought one after another into the range of action of the optoelectronic by means of the feed rollers. This increases the time needed for the evaluation. Even though it would be possible to simultaneously evaluate even more channels by installing additional LEDs, which are arranged in a matrix-like pattern, this would lead to a disproportionate increase in the price of the optoelectronic scanning device, especially because the additional LEDs are not needed during the evaluation of a single channel.
A device for detecting gaseous components, in which individual capsules, which are filled with detection substance and are activated before the beginning of the measurement, has become known from WO 85/00890. The components to be detected enter the interior of the capsules by diffusion and engage in a chemical reaction that can be evaluated with an optoelectronic detection device with the detection substance. Three capsules, which are arranged in parallel and next to one another on the support, can be simultaneously evaluated with the optoelectronic detection device. The reaction of the component to be detected with the detection substance takes place in the capsules due to diffusion of the component into the interior of the capsule. Flow of the component to be detected through individual capsules from a gas inlet to a gas outlet is not provided and is also not possible, because the detection substance occurs as a liquid, which completely fills the capsule.
The primary object of the present invention is to improve a device of the class described such that multi-channel arrangements connected in parallel in terms of flow can also be analyzed in a simple manner with an optoelectronic scanning device that evaluates single channels along a scanning section.
This object is attained by the channels being aligned on the support such that an angle a not equal to zero is formed between the flow axis and the scanning section, and the channels are located in the covered area of the scanning section.
The advantage of the present invention is essentially the fact that due to the channels being arranged at an angle to the detection section, the channels can be simultaneously evaluated within the covered area with a scanning section, and so-called spot measurements (which are performed to determine whether or not a certain component or certain components is/are present in the gas sample) can thus be performed in a particularly simple manner. The channels are arranged in the covered area of the scanning section such that they are always in the active area of the scanning section. If the scanning section consists of, e.g., 6 LEDs for scanning the change in the color of the reaction zones, six channels crossing the scanning section can also be evaluated if these are arranged within the range of action of one LED. The channels can be etched or milled into the support, or they may be designed as a film pack with individual channels or as capillary tubes, in which case, e.g., the capillary tubes are placed into the support. The advantage of a simultaneous evaluation of a plurality of channels for the user is the fact that information on the type of the composition of the gas sample to be investigated can be obtained by a single measurement after a short measurement time, without the support having to be moved within the detection device. Once the substance being sought is identified, the substance can subsequently be quantitatively analyzed by a one-channel measurement, i.e., with a channel extending along the scanning section.
The channels are preferably arranged in a radial pattern on the support, and the channels may originate from a reference point on the support. In the case of the radial arrangement, the angle a between the flow axis and the scanning section is, in general, different from one channel to the next.
The channels may also be arranged in parallel to one another on the support, and an especially simple, advantageous arrangement is obtained by directing the channels at right angles to the scanning section.
The channels are preferably arranged on the support such that the scanning section is located approximately at half the length L of the channels. A change in the color of the reaction zone within one channel extending over at least half the length of the channel can be thus be detected. However, depending on the task, it is also possible to arrange the channels on the support such that the scanning section is located more in the area of the beginning or the end of the channel, wherein the beginning of the channel is defined as the point of inlet of the gas sample to be analyzed into the channel.
Sections of the channels are advantageously bent in the direction of the scanning section. The length of the section is preferably selected to be such that it is located at least between two active sections of the scanning section. If the active sections consist of individual LEDs, the length of the section is at least the distance between two LEDs along the scanning section.
If the scanning device consists of individual optical channels, e.g., an LED array of 6 LEDs, and two LEDs are needed for the evaluation of one section, three channels can be simultaneously evaluated.